Cobalt based interconnects and methods of fabrication thereof

ABSTRACT

An embodiment includes a metal interconnect structure, comprising: a dielectric layer disposed on a substrate; an opening in the dielectric layer, wherein the opening has sidewalls and exposes a conductive region of at least one of the substrate and an interconnect line; an adhesive layer, comprising manganese, disposed over the conductive region and on the sidewalls; and a fill material, comprising cobalt, within the opening and on a surface of the adhesion layer. Other embodiments are described herein.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a Divisional of U.S. patent application Ser.No. 16/881,530, filed May 22, 2020, which is a Continuation of U.S.patent application Ser. No. 15/925,009, filed Mar. 19, 2018, now U.S.Pat. No. 10,700,007, issued Jun. 30, 2020, which is a Continuation ofU.S. patent application Ser. No. 14/137,526 filed Dec. 20, 2013, nowU.S. Pat. No. 9,997,457 issued Jun. 12, 2018, entitled “COBALT BASEDINTERCONNECTS AND METHODS OF FABRICATION THEREOF”, the entire disclosureof which are hereby incorporated by reference in their entirety and forall purposes.

TECHNICAL FIELD

Embodiments of the present invention relate generally to metalinterconnect structures and their methods of fabrication. Moreparticularly, embodiments of the present invention relate to cobaltbased interconnect structures and their methods of fabrication.

BACKGROUND

Integrated circuit (IC) devices typically include circuit elements suchas transistors, capacitors and resistors formed within or on asemiconductor substrate. Interconnect structures are used toelectrically couple or connect the discrete circuit elements intofunctional circuits. Typical metal interconnects may include a lineportion and a via portion.

Interconnect structures may be fabricated from copper, and may include abarrier layer such as titanium or tantalum or nitride materials such astantalum nitride or titanium nitride, or a combination thereof (e.g.,tantalum nitride/tantalum (TNT)). A problem with utilizing copperinterconnect structures is that they are highly susceptible toelectromigration which can lead to void formation and failure.

Tungsten metallization has been successfully used to fabricate front endcontacts and, thus, has been suggested for back end metallization forinterconnect fabrication. A desirable advantage with utilizing tungstenmetallization is that it is highly resistant to detrimentalelectromigration effects. However, a disadvantage with utilizingtungsten metallization is that its electrical resistivity is higher thancopper. More specifically, tungsten line resistances are 4 to 6 timeshigher than copper interconnects, and via resistances can be as much as20% higher. These high resistances severely degrade IC performance andare therefore undesirable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1E are cross-sectional side view illustrations of a method offorming cobalt interconnects according to an embodiment of the presentinvention.

FIG. 2 is a cross-sectional side-view illustration of an integratedcircuit with multiple metallization layers formed with cobaltinterconnects according to an embodiment of the invention.

FIG. 3 is a flow chart illustrating a method of forming cobaltinterconnects according to an embodiment of the present invention.

FIGS. 4A-4D are cross-sectional side view illustrations of a method offorming cobalt interconnects with a cobalt plug according to anembodiment of the invention.

FIGS. 5A-5D are cross-sectional side view illustrations of a method offorming cobalt interconnects with a cobalt plug according to anembodiment of the invention.

FIG. 6 is a flow chart illustrating a method of forming cobaltinterconnects with a cobalt plug according to an embodiment of theinvention.

FIG. 7 depicts a semiconductor field effect transistor (FET) including acobalt-based metal gate electrode, in accordance with an embodiment ofthe present invention.

DETAILED DESCRIPTION

Reference will now be made to the drawings wherein like structures maybe provided with like suffix reference designations. In order to showthe structures of various embodiments more clearly, the drawingsincluded herein are diagrammatic representations ofsemiconductor/circuit structures. Thus, the actual appearance of thefabricated integrated circuit structures, for example in aphotomicrograph, may appear different while still incorporating theclaimed structures of the illustrated embodiments. Moreover, thedrawings may only show the structures useful to understand theillustrated embodiments. Additional structures known in the art may nothave been included to maintain the clarity of the drawings. For example,not every layer of a semiconductor device is necessarily shown. “Anembodiment”, “various embodiments” and the like indicate embodiment(s)so described may include particular features, structures, orcharacteristics, but not every embodiment necessarily includes theparticular features, structures, or characteristics. Some embodimentsmay have some, all, or none of the features described for otherembodiments. “First”, “second”, “third” and the like describe a commonobject and indicate different instances of like objects are beingreferred to. Such adjectives do not imply objects so described must bein a given sequence, either temporally, spatially, in ranking, or in anyother manner. “Connected” may indicate elements are in direct physicalor electrical contact with each other and “coupled” may indicateelements co-operate or interact with each other, but they may or may notbe in direct physical or electrical contact.

One embodiment of the invention is a cobalt interconnect which includesa manganese (Mn) based adhesion layer and a cobalt fill material. Theadhesion layer (sometimes also referred to herein as a barrier layer orwetting layer) may include various Mn based compositions such as, forexample, Mn, manganese nitride (MnN), or manganese silicon nitride(MnSixN_(y)). The Mn based adhesion layer may comprise a film depositedin patterned backend interconnect structures. These interconnectstructures may be metalized with cobalt. The Mn based layer adheres wellto the interlayer dielectric (ILD) that helps form the interconnect insome embodiments. The Mn based layer also provides wetting to the cobaltmetal. Thus, the Mn based adhesion layer helps achieve robust gapfilling of interconnect structures at small scales such as 22 nm, 14 nm,10 nm and beyond.

An embodiment includes a cobalt interconnect that includes a cobalt pluglayer and a cobalt fill material. The plug layer is formed from adifferent composition and/or by a different process than that used tofor the cobalt fill material. Such cobalt interconnects are advantageoussince they have a low resistance (e.g., lower than tungsten) and arehighly resistive to electromigration (e.g., more resistive toelectromigration than copper), enabling fabrication of high performanceinterconnect structures. As dimensions scale in conventionalinterconnect processing, the high resistance of traditional barrierlayers (e.g., TNT barrier layers) can impact the performance ofconventional copper interconnects to greater extents. However, lowerresistance Mn layers may mitigate these resistance issues.

In a first aspect, a conformal Mn based adhesion layer is formed in anopening in a dielectric layer. A cobalt-based fill material is thendeposited or grown on the Mn based adhesion layer to form a cobaltinterconnect.

FIGS. 1A-1E illustrate a method of forming a cobalt interconnect with aMn based adhesion layer and a cobalt-containing fill layer according toembodiments of the present invention. FIG. 1A illustrates a substrate106 with top surface 118 that may be used as a substrate on which acobalt interconnect can be formed. Substrate 106 can include any portionof a partially fabricated IC on which a cobalt interconnect isultimately fabricated. For example, substrate 106 will typicallyinclude, or have formed thereon, active and passive devices. As depictedin FIG. 1A, a conductive region 150 is included in substrate 106, on towhich a cobalt interconnect is ultimately formed. In one suchembodiment, the substrate 106 has been processed through front end ofline (FEOL), and the conductive region 150 is a diffusion region formedin a crystalline semiconductor substrate or layer (e.g., the conductiveregion is a source or drain region of a transistor). In another suchembodiment, the conductive region 150 is an underlying metal line in aback end of line (BEOL) metallization structure, as is described ingreater detail below in association with FIG. 2. Thus, while portion 150is at times referred to herein as a “conductive region 150” this may ormay not indicate that area 150 is any more or less conductive than therest of 106. Also, the use of 150 is not intended to indicate that 150is necessarily nonmonolithic with 106 or was formed with a differentprocess or non-simultaneously with 106. For example, when 106 is aninterconnect line area 150 is monolithic with 106 and structurally andfunctionally indistinguishable from the rest of 106. However, area 150may also be an area doped differently than the rest of 106 when 150 isto serve as a source or drain. The above clarification is provided toavoid excessive figures and to otherwise provide clarity in succinctmanner.

Although embodiments may be ideally suited for fabricating semiconductorICs such as, but not limited to, microprocessors, memories,charge-coupled devices (CCDs), system on chip (SoC) ICs, or basebandprocessors, other applications can also include microelectronicmachines, MEMS, lasers, optical devices, packaging layers, and the like.Embodiments may also be used to fabricate individual semiconductordevices (e.g., a cobalt structure described herein may be used tofabricate a gate electrode of a metal oxide semiconductor (MOS)transistor).

Referring again to FIG. 1A, a dielectric layer 102 is formed abovesubstrate 106. The dielectric layer 102 may be composed of any suitabledielectric or insulating material such as, but not limited to, silicondioxide, SiOF, carbon-doped oxide, a glass or polymer material, and thelike. An opening is formed in the dielectric layer. The opening exposesthe conductive region 150 to which contact (indirect or direct) by acobalt interconnect is ultimately made. In one embodiment, as depictedin FIG. 1A, the opening includes a lower opening 114 (e.g., a via holeor slot) with sidewalls 116 and an upper opening 110 (e.g., a metal linetrench) with sidewalls 112, as is common in a dual damascene process.Although two openings are depicted (or a single opening with varyingwidths), it is to be appreciated that a single opening may instead beformed in the dielectric layer 102 (e.g., as is used in a singledamascene approach where only a line or a via, but not both, isfabricated in a single operation). The opening or openings may befabricated in dielectric layer 102 by well known lithography and etchprocessing techniques typically used in damascene and dual damascenetype fabrication. Although only a single dielectric layer 102 isdepicted, multiple layers of the same or differing dielectric materialsmay instead be used (e.g., a first dielectric layer having opening 114therein, and a second dielectric layer having opening 110 therein).Additionally, in an embodiment, and as depicted in FIG. 1A, thedielectric layer 102 is formed on an etch stop layer 104 disposed onsubstrate 106. The etch stop layer 104 may be composed of a materialsuch as silicon nitride or silicon oxynitride.

Referring to FIG. 1B, a Mn based adhesion layer 120 (e.g., an adhesionlayer including Mn, MnN, MnSi_(x)N_(y) and the like) is deposited. Inother systems a seed layer may be formed on a TNT based adhesion layer.Seed layers, such as the seed layer disclosed in U.S. patent applicationSer. No. 13/730,184, may facilitate formation of fill material. However,no such seed layer is needed in the embodiment of FIG. 1B. Nor isdeposition of an alloy between an adhesion layer and a seed layer neededin the embodiment of FIG. 1B. Thus, as will be seen below, a Mn basedadhesion layer may directly contact ILD 102 and directly contact cobaltfill (described below) without the need for a TNT based adhesion layer,any seed layer, or any alloy layer between a TNT based adhesion layerand a seed layer.

In FIG. 1B the Mn based adhesion layer 120 may be formed on a topsurface 108 of the dielectric layer 102 as well as on the exposed topsurface 118 of the substrate 106 (e.g., on conductive region 150). While106 is referred to as “substrate” in another embodiment 106 could be ametal interconnect line, and the like. The Mn based adhesion layer 120is also formed on the sidewalls 116 of the upper opening 114, and thesidewalls 112 of the lower opening 110.

Mn based adhesion layer 120 may be a conformal layer composed of amaterial including Mn, MnN, MnSi_(x)N_(y), MnSi_(x)O_(y) (e.g.,Mn₂[SiO₄], MnSiO₃), other Mn based silicates, and the like. In anembodiment with the adhesion layer including Mn, the Mn content mayinclude 90-100% Mn, where contamination (i.e., the remaining 10%) mayinclude C, H, 0 and combinations thereof. In an embodiment with theadhesion layer including MnN_(x), the Mn may compose 0-50% Mn and the Nmay compose 0-50%. In an embodiment with the adhesion layer includingMnN_(x), the adhesion layer may include Mn₄N or Mn₃N₂. In an embodimentwith the adhesion layer including MnN_(x)Si_(y) the Mn and N may includeup to 50% with the Si constituting the remainder of the material. In anembodiment Mn, N, and Si may be included with one another in variousadhesion multilayer combinations such as bilayers or trilayers (e.g., anadhesion layer includes one sublayer including MnN and another sublayerincluding Mn), (e.g., one adhesion layer including a sublayer having Mnand N and another sublayer including primarily Mn), (e.g., one adhesionlayer including a sublayer including MnN_(x)Si_(y) and another sublayerincluding primarily Mn), and the like. As used herein, % of compositionrefers to atomic %.

In one embodiment, the Mn based adhesion layer 120 is formed to athickness less than 3 nm, and typically 1 nm to 3 nm. In an embodimentthickness ranges for layer 120 (whether layer 120 includes a singlelayer or multiple sublayers such as one sublayer including MnN andanother immediately adjacent sublayer including Mn) may range from 0.1 Ato 50 A. In an embodiment layer 120 is between 10 A-20 A including, forexample, 10, 12, 14, 16, 18, or 20 A.

In an embodiment, conductive region 150 includes at least some germanium(e.g., an exposed doped silicon germanium or doped germanium region, ora metal germanide region). In an embodiment, conductive region 150includes at least some silicon (e.g., an exposed doped silicon region,or a metal silicide region).

The layer 120 may be deposited or grown by chemical vapor deposition(CVD), atomic layer deposition (ALD), physical vapor deposition (PVD),electroplating, electroless plating or other suitable process thatdeposits conformal thin films. In an embodiment, the layer 120 isdeposited to form a high quality conformal layer that sufficiently andevenly covers all exposed surfaces within the openings and top surfaces.The adhesion layer may be formed, in one embodiment, by depositing theMn based material at a slow deposition rate to evenly and consistentlydeposit the conformal adhesion layer. By forming the layer 120 in aconformal manner, compatibility of a subsequently formed fill material(such as cobalt) with the underlying structure may be improved.Specifically, the layer 120 can assist a deposition process by providingappropriate surface energetics for deposition thereon.

Deposition recipes of thin films using processes such as CVD, ALD, andPVD may vary depending on the desired process time, thickness, andquality of conformity. For example, utilizing CVD to deposit theadhesion layer 120 may create a conformal thin film layer more quicklythan it would take an ALD process to deposit the same layer; however,the quality of the thin film deposited by the CVD process may be lowerthan the quality of the thin film deposited by the ALD process. Inanother embodiment, the layer 120 is deposited by a PVD process. The PVDprocess may be performed with an increased distance between thereceiving substrate and the corresponding sputter target to form ahighly conformal thin film.

Referring to FIG. 1C, a fill material 122 may be formed on the exposedsurfaces of the adhesion layer 120, such that the fill material 122completely fills the openings 110 and 114 and is formed on the topsurface of the adhesion layer 120 and on the top surface 108 ofdielectric 102. A seam 124 may be formed within the openings 110, 114during deposition of the fill material 122. In an embodiment, the fillmaterial 122 is composed of a dilute alloy composed of approximately0.25-5% of a non-cobalt element (e.g., Al, Ni, Cu, Ag, Au, Mn, Ti, V,Cr, Fe, Ta, W, Ru, P, B, C, N, Si, Ge, Mg, Zn, Rh, Pt, Cd, Hf, In, Sn,C, O, Be, Ca, Zr, Nb, Mo, Ir, Re, or Pd) with the remainderapproximately 95+% cobalt. Such a dilute alloy can involve, eitherduring deposition or processing subsequent to deposition, migration ofthe non-cobalt species to surfaces of fill 122. The migration canprovide a diffusion barrier for the cobalt (in addition toadhesion/barrier layer 120) and/or be used to enhance adhesion of thecobalt to layer 120. Grain boundaries within the cobalt may also befilled by the non-cobalt species. In one embodiment, the fill material122 consists essentially only of cobalt. In another embodiment, the fillmaterial 122 is at least 90% cobalt. In yet another embodiment, the fillmaterial 122 is composed of at least 50% cobalt.

In an embodiment of the invention, the cobalt fill material 122 may beformed by a process such as, but not limited to, CVD, ALD, PVD,electroplating, or electro-less plating. In one embodiment, the processmethod used to form the fill material 122 may be different than theprocess used to form the layer 120. Furthermore, the layer 120 may beformed conformally, while the fill material 122 is formed in anon-conformal or bottom up approach. For example, the layer 120 may beformed by an ALD deposition process that forms a conformal layer onexposed surfaces of the receiving substrate, while the fill material 122may be formed by PVD process that directionally sputters the fillmaterial onto the surfaces of the layer 120, with greater depositionrates on flat horizontal surfaces as opposed to on more verticallyoriented sidewall surfaces. In another example, the layer 120 may beformed by an ALD deposition process that forms a conformal layer onexposed surfaces of the receiving substrate, while the fill material 122may be formed by an electroplating process that grows the fill materialfrom the surfaces of the layer 120. In yet another example, the layer120 may be formed by a CVD deposition process and the fill material maybe formed by a PVD process.

In another embodiment, the layer 120 and the fill material 122 may bedeposited by the same process (e.g. ALD, CVD, or PVD) but with differentsets of deposition parameters, such as pressure, deposition rate,temperature, and the like. For example, the layer 120 and the fillmaterial 122 may be deposited by a CVD process; however, the set ofparameters used in the CVD processing for the adhesion layer 120, suchas deposition pressure and temperature, may be different than the set ofparameters used in the CVD processing for the fill material 122. Inanother example, the layer 120 and the fill material 122 are formed by aPVD process, but the layer 120 may be formed by a PVD process with alarger distance between the target and the receiving substrate than thePVD process used to form the fill material 122. In another embodiment,the metal fill material 122 is formed by a colummated PVD process, whilethe layer 120 is formed by a non-colummated PVD process. Oralternatively, the layer 120 is formed by an ALD process with a lowerdeposition rate than the deposition rate of the ALD process used to formthe fill material 122 such that the layer 120 is formed more conformallythan the fill material 122.

Referring to FIG. 1D, an anneal process may optionally be performed toreflow the deposited interconnect layer. The seam 124 from FIG. 1C maybe removed subsequent to the anneal process, forming a solid structurewithin openings 110 and 114 within dielectric layer 102. The annealprocess may help grow larger grain structures within the fill material122, decreasing resistivity and expelling impurities from poor grainstructures. In one embodiment, the anneal process uses gasses such asnitrogen, hydrogen, and argon. Furthermore, the anneal process may beperformed at a temperature less than the thermal budget of the backendstructures. For example, in one embodiment, the anneal process isperformed at a temperature of room temperature to 300° C., 400° C., 500°C. or more. In another embodiment, the anneal process is performed at atemperature that is higher than the melting point of fill material 122but lower than the thermal budget of the backend structures. In variousembodiments the anneal process can vary widely (e.g., room temperatureto 300° C., 400° C., 500° C. or more for interconnects ranging up to900° C. for Front end applications). In such embodiments the annealtemperature is not higher than the melting point of the material beingannealed as reflow of materials to be annealed can happen at much lowertemperatures than the melting point for the material to be annealed. Insuch embodiments anneal temperatures for the material to be annealed maybe less than the thermal budget of backend structures.

In yet another embodiment, a cycling technique may optionally beutilized to deposit the interconnect layer 122 (also referred to as filllayer 122) within the openings 114 and 110 without the seam 124. Onecycle may involve one deposition of the fill material 122 and one annealprocess. The anneal operation of one cycle may be set at a temperatureand time duration to briefly reflow the fill material to improve stepcoverage. The deposition operation of one cycle may be a shortdeposition to deposit less fill material, such that several operationsare required to completely fill the via and line openings 114 and 110.In one embodiment, less than 5 cycles are needed to deposit the fillmaterial 122 without a seam 124.

Referring to FIG. 1E, a chemical mechanical planarization (CMP) processmay be performed to remove the fill material 122 and the adhesion layer120 disposed above the top surface 108 of the dielectric layer 102. Inone embodiment, the CMP process may be a timed CMP process that is timedto stop at the top surface 108 of the line dielectric layer. In anotherembodiment, the CMP process may utilize the top surface 108 of the linedielectric layer as a stopping layer. Because the thickness of the fillmaterial deposited above the top surface of the line dielectric layermay vary, utilizing the top surface 108 as a stopping layer may be amore reliable method. In an alternative embodiment, an etch process isused to remove the fill material 122 and the layer 120 disposed abovethe top surface 108 of the dielectric layer 102.

FIG. 2 illustrates a cross-section 200 of a portion of an IC structurewith cobalt metal interconnects according to an embodiment of thepresent invention. A stack of dielectric layers 102 includes metalinterconnects having adhesion layers 120 and metal (e.g., cobalt) filllayers 124. The portion of the IC structure shown in FIG. 2 can be aportion of a back end of line (BEOL) metallization structure as found,for example, in a microprocessor die or memory die.

FIG. 3 is a flow chart 300 illustrating a method of forming a cobaltmetal interconnect according to an embodiment of the present invention.At 302, an opening is formed in a dielectric layer to expose aconductive region in a substrate (or on an additional metalinterconnect). At 304, a Mn based adhesion/barrier layer is formed overthe substrate, in contact with the conductive region, as well as overthe dielectric layer and on sidewalls of the opening. At 306, a fillmaterial is formed on the adhesion layer and fills the opening. The fillmaterial is composed of a cobalt-based material. At 308, in an optionalembodiment, heat is applied to reflow the fill material. At 310, thefill material and adhesion layer material disposed above an uppersurface of the dielectric layer are removed.

In an embodiment a cobalt-based plug is formed in a lower portion (e.g.,a via hole or slot) of an opening in a dielectric layer. A cobalt-basedconductive line is then formed on the cobalt-based plug, in an upperportion (e.g., a metal line trench) of the opening, to form a cobaltinterconnect.

For example, FIGS. 4A-4D illustrate a method of forming a cobalt metalinterconnect according to an embodiment of the invention. The methodbegins with the same structure as illustrated and described inassociation with FIG. 1B, which includes adhesion layer 120 and will notbe described again for the sake of brevity.

Referring to FIG. 4A, a plug 420 is formed on adhesion layer 120. In anembodiment, as depicted, the plug 420 is formed only within the loweropening 114 of the dielectric layer 102 such that the lower opening 114is completely filled with plug material 420. In another embodiment,however, the top surface of the plug 420 may not be planar with the topsurface of the lower opening 114. For example, the top surface of theplug 420 may be higher or lower than the top surface of the loweropening. The top surface of the plug 420 may be at, above, or below thehorizontal top surface of layer 120 where layer 120 is horizontallydisposed at the top of 114 and bottom of 110. As depicted in FIG. 4A theplug 420 has a top surface just below the horizontal top surface oflayer 120 where layer 120 is horizontally disposed at the top of 114 andbottom of 110. In another embodiment, the top surface of the plug 420may form a mushroom-like dome as a result of the growth profile duringformation of plug 420.

In an embodiment, plug 420 is formed in a bottom-up approach. That is,the plug 420 is not formed by conformal deposition. For example, in oneembodiment, the formation of plug 420 is performed by selectivelydepositing on, and then growing from, the surface of layer 120 directlyabove the conductive region 150. In a specific embodiment, the plug 420is formed by electrolessly plating the plug material onto an exposed andcompatible surface of layer 120. As an example, the conductive region150 has an upper metalized or metal-containing surface such as cobalt(Co), copper (Cu) or Tungsten (W), and a cobalt-based plug 420 is formedby electroless deposition involving bottom-up growth from the layer 120above the metalized or metal-containing surface of conductive region150. In other embodiments, other suitable bottom-up fill and growthdeposition approaches may be used such as, but not limited to,electroplating. A bottom-up fill approach is one in which a depositionrate is faster on planar or flat surfaces than on vertical sidewallsurfaces.

The plug 420 may be a cobalt-based plug composed of at least 50% cobalt.In a particular embodiment, the plug 420 is composed of at least 90%cobalt. In any such cases, the non-cobalt remainder of the plug 420composition, if any, can include one or more of Al, Ni, Cu, Ag, Au, Mn,Ti, V, Cr, Fe, Ta, W, Ru, P, B, C, N, Si, Ge, Mg, Zn, Rh, Pt, Cd, Hf,In, Sn, C, O, Be, Ca, Zr, Nb, Mo, Ir, Re, or Pd. In another embodiment,the plug 420 is composed of a cobalt-based compound or alloy material.For example, in one embodiment, the plug 420 is composed of a dilutealloy composed of approximately 0.25-5% of a non-cobalt element, such asthose listed above, with the remainder approximately 95+% cobalt, isused. Such a dilute alloy can involve, either during deposition orprocessing subsequent to deposition, migration of the non-cobalt speciesto surfaces or interfaces of the cobalt plug. The migration can providea diffusion barrier for the cobalt and/or be used to enhance adhesion ofthe cobalt to layer 120. Grain boundaries within the cobalt may also befilled by the non-cobalt species. In other embodiments, however, theplug 420 may include less than 50% cobalt, but still be referred to as acobalt-based material. Exemplary embodiments of cobalt-based compoundplug 420 materials include cobalt silicide or cobalt germanide plugmaterials. In a specific such embodiment, conductive region 150 includesat least some germanium (e.g., an exposed doped silicon germanium ordoped germanium region, or a metal germanide region), and the plug 420material is a cobalt germanide layer. In another specific suchembodiment, conductive region 150 includes at least some silicon (e.g.,an exposed doped silicon region, or a metal silicide region), and theplug 420 material is a cobalt silicide layer. Exemplary embodiments ofcobalt-based alloy plug 420 materials include cobalt alloyed with one ormore of the following: Al, Ni, Cu, Ag, Au, Mn, Ti, V, Cr, Fe, Ta, W, Ru,P, B, C, N, Si, Ge, Mg, Zn, Rh, Pt, Cd, Hf, In, Sn, C, O, Be, Ca, Zr,Nb, Mo, Ir, Re, or Pd. In the above described embodiments, the cobaltplug 420 may have a small grain structure. In an embodiment the abovementioned dopant (i.e., the 0.25-5% of a non-cobalt element) could beused without layer 120 so that cobalt would adhere directly to sidewall116 as well as portion 150. In an embodiment the dopant essentiallycreates a layer 120 (an adhesion layer) by diffusion to interfaces suchas interfaces at 150 and 116. In one embodiment the dopant forms a layerwith portion 150. In another embodiment the dopant makes no layerformation with 150 so that the barrier is bottomless and plug 420directly contacts area 150.

Referring to FIG. 4B, pretreatment 422 may optionally be performed onthe exposed top surface of the plug 420 and layer 120. Pretreatment maybe performed by a plasma process or ion bombardment to enhance adhesionof a later formed compound to the treated surface. In one embodiment,pretreatment may be performed in a plasma chamber at a temperatureranging from room temperature up to approximately 300° C., 400° C., 500°C. or more for approximately 20 to 60 seconds utilizing, for example,H₂/He plasma, Ar plasma, NH₃ plasma, N₂ plasma, and/or combinationsthereof. In another embodiment, the pretreatment may include Ar ionbombardment. It is to be understood that such pretreatment may beperformed at other stages of the process flow (e.g., prior to formingplug materials). In an embodiment the pretreatment is performed beforelayer 120 is formed. However, in other embodiments a treatment of layer120 can be quite beneficial to density without affecting dielectricssuch as layer 102.

Referring to FIG. 4C, a fill material 424 is formed on the plug 420 andlayer 120 within upper opening 110. A seam 426 may be formed within theupper opening 110 subsequent to deposition of the fill material 424. Inone embodiment, fill material 424 is composed of a material comprisingcobalt. For example, fill material may be composed of, and deposited by,materials and processes described above for fill material 122.Furthermore, the fill material 424 may differ from the plug 420 materialby composition and/or deposition technique.

An anneal process may optionally be performed to reflow the depositedfill material 424. The seam 426 from FIG. 4C may be removed subsequentto the anneal process, forming a solid structure within openings 110 and114 within dielectric layer 102. The anneal process may enable growth oflarger grain structures within the fill material 424, decreasingresistivity and expelling impurities from otherwise poor grainstructures. In one embodiment, the anneal process involves use of aforming gas such as, but not limited to, nitrogen, hydrogen, or argon.Furthermore, the anneal process may be performed at a temperature lessthan the thermal budget of the backend structures. For example, in oneembodiment, the anneal process is performed at a temperature of roomtemperature to 300° C., 400° C., 500° C. or more. In another embodiment,the anneal process is performed at a temperature that is higher than themelting point of fill material 424 but lower than the thermal budget ofthe backend structures. In embodiments the anneal temperature is nothigher than the melting point of the material being annealed as reflowof materials to be annealed can happen at much lower temperatures thanthe melting point for the material to be annealed. In such embodimentsanneal temperatures for the material to be annealed may be less than thethermal budget of backend structures.

In yet another embodiment, a cycling technique is optionally utilized todeposit the fill material 424 within the opening 110 without the seam426. One cycle may involve a single deposition of the fill material 424and a single anneal process. The anneal operation of one cycle may beset at a temperature and time duration to briefly reflow the fillmaterial 424 to improve step coverage. The deposition operation of onecycle may be a short deposition to deposit less fill material 424, suchthat several operations are required to completely fill the upperopening 110. In one embodiment, less than 5 cycles are needed to depositthe fill material 424 without a seam 426.

Referring to FIG. 4D, a CMP process may be performed to remove the fillmaterial 424 above the top surface of layer 120 to provide thecobalt-based structure 428. In one embodiment, the CMP process may be atimed CMP process that is timed to stop at the top surface 108 of theline dielectric layer. In another embodiment, the CMP process mayutilize the top surface 108 of the dielectric layer 102 as a stoppinglayer. Because the thickness of the fill material deposited above thetop surface 108 of the dielectric layer 102 may vary, utilizing the topsurface 108 as a stopping layer may be a more reliable method. In analternative embodiment, an etch process is used to remove the fillmaterial 424 above the top surface 108 of the dielectric layer 102.

In an embodiment a cobalt-based plug is formed in a lower portion (e.g.,a via hole or slot) of an opening in a dielectric layer. An adhesivelayer is then formed in an upper portion (e.g., a metal line trench) ofthe opening, over the cobalt-based plug. A cobalt-based conductive lineis then formed on the portion of the adhesive layer that is directlyover the plug to fill the upper portion of the opening to form a cobaltinterconnect.

For example, FIGS. 5A-5D illustrate a method of forming a cobaltinterconnect with a Mn based adhesion layer and a cobalt containing filllayer according to an embodiment of the invention. The method beginswith the same structure as illustrated and described in association withFIG. 1A. Next, referring to FIG. 5A, the cobalt-based plug 420 is formedin the lower opening 114 of the dielectric layer 102, on the conductiveregion 150 of substrate 106. However, in another embodiment the adhesionlayer be first formed along the side walls of dielectric 102 and/or ontop of portion 150 before plug 420 is formed.

Referring to FIG. 5B, a Mn based adhesion layer 524 (e.g., Mn, MnN,MnSi_(x)N_(y) MnSi_(x)O_(y) (e.g., Mn₂[SiO₄], MnSiO₃), other Mn basedsilicates, and the like) is deposited conformally with the structure ofFIG. 5A. For example, in one embodiment, the Mn based adhesion layer 524is formed in the upper opening 114 of the dielectric layer 102 and onthe exposed plug 420. The composition and method of forming the adhesionlayer 524 may be as described for adhesion layer 120 of FIG. 1B.

Referring to FIG. 5C, a fill material 526 is formed on the adhesionlayer 524, within upper opening 110, and on the top surface 108 of thedielectric layer 102. A seam 528 may be formed within the opening 110subsequent to deposition of the fill material 526. The composition andmethod of forming the fill material layer 526 may be as described forfill material 122 of FIG. 1C. Furthermore, although in an embodiment theplug 420 and the fill material 526 are all cobalt-based, they may alldiffer from one another by composition and/or deposition technique.

An anneal process may optionally be performed to reflow the depositedfill material 526. The seam 528 from FIG. 5C may be removed subsequentto the anneal process, forming a solid structure within opening 110 ofdielectric layer 102. The anneal process may enable growth of largergrain structures within the fill material 526, decreasing resistivityand expelling impurities from poor grain structures. In one embodiment,the anneal process involves a use of gas such as, but not limited to,nitrogen, hydrogen, or argon. Furthermore, the anneal process may beperformed at a temperature less than the thermal budget of the backendstructures. For example, in one embodiment, the anneal process isperformed at a temperature of room temperature to 300° C., 400° C., 500°C. or more. . In another embodiment, the anneal process is performed ata temperature that is higher than the melting point of fill material 526but lower than the thermal budget of the backend structures. Inembodiments the anneal temperature is not higher than the melting pointof the material being annealed as reflow of materials to be annealed canhappen at much lower temperatures than the melting point for thematerial to be annealed. In such embodiments anneal temperatures for thematerial to be annealed may be less than the thermal budget of backendstructures.

In yet another embodiment, a cycling technique may be utilized todeposit the fill material 526 within the opening 110 without the seam528. One cycle may involve one deposition of the fill material 526 andone anneal process. The anneal operation of one cycle may be set at atemperature and time duration to briefly reflow the fill material toimprove step coverage. The deposition operation of one cycle may be ashort deposition to deposit less fill material, such that severaloperations are required to completely fill the opening 510. In oneembodiment, less than 5 cycles are needed to deposit the fill material526 without a seam 528.

Referring to FIG. 5D, a CMP process may be performed to remove the fillmaterial 526 and the adhesion layer 524 disposed above the top surface108 of the dielectric layer 102 to provide the cobalt-based structure530. In one embodiment, the CMP process may be a timed CMP process thatis timed to stop at the top surface 108 of the dielectric layer 102. Inanother embodiment, the CMP process may utilize the top surface 108 ofthe dielectric layer 102 as a stopping layer. Because the thickness ofthe fill material deposited above the top surface 108 of the dielectriclayer 102 may vary, utilizing the top surface 108 as a stopping layermay be a more reliable method. In an alternative embodiment, an etchprocess is used to remove the fill material 526 and the layer 524disposed above the top surface 108 of the dielectric layer 102.

FIG. 6 is a flow chart 600 illustrating a method of forming a cobaltmetal interconnect according to an embodiment of the present invention.At 602, an opening is formed in a dielectric layer to expose aconductive region in a substrate. At 604, a cobalt plug is formed in alower portion of the opening, in contact with the conductive region. At605 a Mn based adhesion layer (e.g., Mn, MnN, MnSi_(x)N_(y) and thelike) is formed in the upper portion of the opening. At 606, a fillmaterial is formed on the plug and adhesion layer to fill the opening.The fill material is composed of a cobalt-based material. At 608, in anoptional embodiment, heat is applied to reflow the fill material. At610, the fill material disposed above an upper surface of the dielectriclayer is removed. In one such embodiment, the fill material and the plugboth include cobalt, but have different material compositions. Inanother such embodiment, the fill material and the plug both includecobalt, but are formed by different deposition or growth techniques. Inyet another such embodiment, the fill material and the plug both includecobalt, but have different material compositions and are formed bydifferent deposition or growth techniques.

In an embodiment a metal gate electrode of a semiconductor device iscomposed, as least partially, of cobalt. That is, embodiments of thepresent invention need not be limited to forming cobalt-basedinterconnects.

In an example, FIG. 7 depicts a metal oxide semiconductor field effecttransistor (MOS-FET) 700 fabricated on a substrate 702, in accordancewith an embodiment of the present invention. A gate dielectric layer 704is disposed above a channel region 706, and a gate electrode 708 isdisposed above gate dielectric layer 704. Gate dielectric layer 704 andgate electrode 708 may be isolated by gate isolation spacers 710. Tipextensions 712 may be formed by implanting dopant atoms into substrate702. Source and drain regions (e.g., strain-inducing source/drainregions 720) may be formed by selectively growing an epitaxial film inetched-out portions of substrate 702 and are doped either in situ orafter epitaxial film growth, or both. In an embodiment tip extensions712 may be formed simultaneously with the source and drain regions tocreate “epi” tip extensions. In typical MOS-FETs, the channel region 706is composed of a semiconductor material, such as single crystallinesilicon. In an embodiment, the gate electrode 708 is a metal gateelectrode (e.g., the workfunction of the gate electrode 708 is based ona metal or metal-containing layer). In one such embodiment, the metalgate electrode is composed, at least somewhat, of cobalt. For example,in a specific embodiment, the metal gate electrode 708 includes a Mnbased adhesion layer (e.g., Mn, MnN, MnSi_(x)N_(y) and the like asdescribed above) 708A and a cobalt fill metal thereon 708B. For example,the cobalt-based material or film 708B is composed of at least 90%cobalt. In a specific such embodiment, the cobalt-based material or film708B is composed of a dilute alloy having approximately 0.25-5% of anon-cobalt element, with the remainder approximately 95+% cobalt.

Also, it is to be understood that the MOS-FET 700 may be a planar deviceor include a three-dimensional body (e.g., as in a double-gate, fin-fet,tri-gate, or gate-all-around transistor). As such, the substrate 702 maybe a planar substrate or depict a cross-sectional view of athree-dimensional body. Finally, it is to be understood that onlyseveral features of the MOS-FET 700 are depicted for clarity. It is tobe understood that isolation layers, e.g., interlayer dielectric layer740, and metallization routing layers used for integrating MOS-FET 700into, e.g., an integrated circuit may also be included, as is well knownin the art.

Various cobalt based embodiments may be included in, for example, amobile computing node such as a cellular phone, Smartphone, tablet,Ultrabook®, notebook, laptop, personal digital assistant, and mobileprocessor based platform.

Example 1 includes a dielectric layer disposed on a substrate; anopening in the dielectric layer, wherein the opening has sidewalls andexposes a conductive region of at least one of the substrate and anadditional interconnect structure; an adhesive layer, comprisingmanganese, disposed over the conductive region and on the sidewalls; anda fill material, comprising cobalt, within the opening and on a surfaceof the adhesion layer. In an embodiment the dielectric directly contactsthe substrate but in other embodiments one or more layers are betweenthe dielectric and the substrate. In an embodiment the additionalinterconnect structure may include a via, a trench filled with metal(interconnect line), and the like. While examples have included dualdamascene approaches the opening addressed immediately above need nothave varying widths such as those found in, for example, FIG.1 or theline over via commonly associated with dual damascene processes. Asexplained below, saying “an adhesive layer, comprising manganese,disposed over the conductive region” does not necessarily mean manganesewill be in the portion of the adhesive layer that is over the conductiveregion. For example, “an adhesive layer, comprising manganese, disposedover the conductive region” is still satisfied if manganese in not inthe adhesion layer portion over the conductive region but is in theadhesion layer that is on the sidewalls.

In example 2 the subject matter of Example 1 can optionally includewherein the fill material is composed of at least 50 atomic % cobalt.

In example 3 the subject matter of Examples 1-2 can optionally includewherein the adhesion layer includes at least one element selected from agroup consisting of silicon, nitrogen, carbon, hydrogen, and oxygen.

In example 4 the subject matter of Examples 1-3 can optionally includewherein the adhesion layer is no thicker than 50 A.

In example 5 the subject matter of Examples 1-4 can optionally includewherein the adhesion layer directly contacts the fill material.

In example 6 the subject matter of Examples 1-5 can optionally includewherein the adhesion layer directly contacts the conductive region. Inanother version of example 6 the subject matter of Examples 1-5 canoptionally include wherein the adhesion layer directly contacts theconductive region and the dielectric layer.

In example 7 the subject matter of Examples 1-6 can optionally includewherein the fill material includes at least one element selected from agroup consisting of silicon and manganese. This may be due to silicon ormanganese migrating from the adhesion layer into the fill materialand/or this may be due to the fill material being deposited with siliconand/or manganese already present in addition to cobalt.

In example 8 the subject matter of Examples 1-7 can optionally includewherein the fill material includes manganese that directly contacts themanganese included in the adhesion layer. The cobalt fill layer mayinclude manganese and/or silicon. This may not be visually evident witha scanning electron microscopic (SEM) image or transmission electronmicroscopic (TEM) image but other detection methods may indicate thepresence of manganese and/or silicon in the cobalt fill layer. Themanganese and/or silicon may be present along the outer edge of thecobalt fill layer because the manganese and/or silicon may have migratedfrom the adhesion layer to the cobalt fill layer. For example, there issolubility between manganese and cobalt and the manganese from theadhesion layer, in contact with the fill layer, may have mixed with thecobalt fill layer. This migration helps the cobalt fill adhere to theadhesion layer and also allows the adhesion layer to function as awetting layer for the cobalt fill layer. A wetting layer includes aninitial layer of atoms epitaxially grown on a surface upon whichself-assembled quantum dots or thin films are created.

An example concerns TEM energy dispersive x-rays (EDX). The small TEMprobe electrons interact with material being imaged and that materialemits x-rays from the different elements present within one pixel of theimage. This allows for elemental maps of the image. Higher sensitivityis achieved by taking line scans across structures with more dwell time(e.g., across a via rather than every pixel in image). In an embodiment(example 8a) if there is manganese in the cobalt fill layer, themanganese may migrate to the adhesion layer/fill material interfaceimproving adhesion. EDX may then detect manganese in the cobalt filllayer and around the adhesion layer/fill layer edge/interface. In anembodiment (example 8b) if manganese is at the adhesion layer/fill layerinterface it might diffuse into cobalt and other interfaces (e.g., liketop layer after CMP has been performed). Such a case would be detectedin both the fill layer and around edges/interfaces. In an embodiment, ifno diffusion of manganese occurs the manganese may only be in the filllayer of example 8a and at the interface in example 8b. In embodiment,if manganese is present both in 120 and the fill layer, the manganesemay be detected in both areas. Diffusion may change relativeconcentrations/compositions and ability to adhere or wet so theprocesses of examples 8a and/or 8b take place but manganese may still bedetectable in both scenarios in an embodiment.

An embodiment is similar to the embodiment of FIG. 5D but includes adielectric capping layer/etch stop (e.g., similar or directly equal tothe materials and structure of element 104) that extends from the topsurface on the left dielectric portion 102, across the tops of 524 and526, and then across the top of the right dielectric portion 102. Thiscaps the polished metal and is later broken through by etch to form avia for a next layer just like shown with a via going through space 116and through layer 104 in FIG. 5D. The cap protects the lines (e.g.,material 530) hermetically and manganese (which in this embodiment ismixed and present in cobalt fill 530) would diffuse to the capping layerto improve adhesion of dielectric capping layer/etch stop to the cobalt530 (e.g., by silicate formation). The manganese may diffuse from layer120 or diffuse from an alloy cobalt fill layer that was depositedalready including some amount of manganese. The dielectric cap may bedeposited at a high temperature and so that temperature drives thethermal diffusion of manganese from within the layers 120 and/or 530and/or 420 up to the top of the trench 110. The manganese could bedetected at the new dielectric cap/layer 530 interface by TEM EDXmethods and the like.

In another example the subject matter of Examples 1-8 can optionallyinclude a dielectric layer formed directly on top of the adhesive layerand the fill material, the dielectric layer comprising manganese;wherein the fill material also includes manganese. The manganese mayhave migrated from the adhesion layer and/or adhesion layer into thedielectric.

In another example 9 the subject matter of Examples 1-8 can optionallyinclude a dielectric layer formed directly on top of the fill material,the dielectric layer comprising a first material; wherein the firstmaterial is also included in the fill material and the first material isselected from the group comprising Al, Ni, Cu, Ag, Au, Mn, Ti, V, Cr,Fe, Ta, W, Ru, P, B, C, N, Si, Ge, Mg, Zn, Rh, Pt, Cd, Hf, In, Sn, C, O,Be, Ca, Zr, Nb, Mo, Ir, Re, and Pd. The material may have migrated intothe dielectric from the fill material.

In example 9 the subject matter of Examples 1-8 can optionally includewherein (a) the adhesion layer includes a first portion directlycontacting the dielectric layer and second portion directly contactingthe conductive region, and (b) the first portion includes a higheratomic % manganese than the second portion. Manganese bonds well withthe dielectric as well as the cobalt fill layer. On the adhesionlayer/dielectric interface manganese forms MnSi_(x)O_(y) (e.g.,Mn₂[SiO₄], MnSiO₃), and other Mn based silicates. The silicate has thefunction of a diffusion barrier, preventing diffusion of cobalt into thesurrounding dielectric and will also will have adhesive/wettingfunctions making sure cobalt adheres well to the dielectric. On theadhesion layer/cobalt fill layer interface metal-to-metal bonding occurs(e.g., between the manganese and cobalt) and results in some alloying atthe interface. This bonding gives an additional benefit that manganesewill dissolve at the via bottom (where in an embodiment the adhesionlayer directly contacts the metal fill layer and possibly anotherinterconnect or a conduction substrate portion). This lowers electricalresistance in the via at the adhesion layer interface to the otherinterconnect or conductive portion of the substrate. For example, themanganese from 120 that forms at the via bottom initially starts out asthick as similar 120 portions on ILD. After anneal the manganese maydiffuse completely into the cobalt fill or may remain in layer 120. Theamount that remains may vary. Thus, in some embodiments the adhesionlayer near the bottom of the via may have little to no manganeseremaining after device processing is complete.

In example 10 the subject matter of Examples 1-9 can optionally includewherein the fill material consists essentially of cobalt. In anotherexample the subject matter of Examples 1-9 can optionally includewherein the adhesion layer does not completely separate the conductiveregion from the fill material and the fill material directly contacts aportion of the conductive region. Thus, by TEM EDX detection orotherwise (regardless of whether the adhesion layer completely orincompletely separates the fill material from the conductive region);there may be areas where no manganese in an adhesion layer separates thefill material from the conductive region. This may be deemed an areawhere there is no adhesion layer present that can be detected(regardless of whether the layer is there or not) and thus the “adhesionlayer does not completely separate the conductive region from the fillmaterial and the fill material directly contacts a portion of theconductive region.”

Example 11 includes a method of forming a metal interconnect structure,comprising: forming an opening in a dielectric layer on a substrate,wherein the opening exposes a conductive region of at least one of thesubstrate and an additional interconnect structure; forming an adhesionlayer, comprising manganese, in the opening and on the conductive regionand also on the sidewalls; forming a fill material, comprising cobalt,within the opening and on a surface of the adhesion layer; and removingportions of the fill material and the adhesion layer above an uppersurface of the dielectric layer.

In example 12 the subject matter of Example 11 can optionally includewherein the adhesion layer includes at least one element selected from agroup consisting of silicon, nitrogen, carbon, hydrogen, and oxygen.

In example, 13 the subject matter of examples 11-12 can optionallyinclude wherein the adhesion layer directly contacts the fill material.

In example 14 the subject matter of Examples 11-13 can optionallyinclude wherein the adhesion layer directly contacts the conductiveregion.

In example 15 the subject matter of Examples 13-14 can optionallyinclude wherein (a) the adhesion layer includes a first portion directlycontacting the dielectric layer and second portion directly contactingthe conductive region, and (b) the first portion includes a higheratomic % manganese than the second portion.

In example 16 the subject matter of Examples 13-15 can optionallyinclude forming the adhesion layer with a conformal method and formingthe fill layer with a method that is non-conformal.

In another example the subject matter of Examples 13-15 can optionallyinclude forming a dielectric layer directly on top of the adhesive layerand the fill material, the dielectric layer comprising manganese;wherein the fill material also includes manganese. Again, the manganesemay have migrated into the dielectric from the adhesive layer and/orfill material.

Example 17 includes a metal interconnect structure, comprising: adielectric layer disposed on a substrate; an opening disposed in thedielectric layer and exposing a conductive region in at least one of thesubstrate and an additional interconnect structure, the opening having alower portion and an upper portion; a plug comprising cobalt disposed inthe lower portion of the opening; an adhesive layer, comprisingmanganese, disposed on the sidewalls; and a fill material comprisingcobalt disposed on the plug and in the upper portion of the opening.

In example 18 the subject matter of Example 17 can optionally includewherein the adhesive layer directly contacts the plug and thedielectric.

In example 19 the subject matter of Examples 17-18 can optionallyinclude wherein the adhesive layer is between the plug and the fillmaterial.

In example 20 the subject matter of Examples 17-19 can optionallyinclude wherein the plug and fill material have different compositions.

In another example 20 the subject matter of Examples 17-19 canoptionally include a dielectric layer formed directly on top of theadhesive layer and the fill material, the dielectric layer comprisingmanganese; wherein the fill material also includes manganese. Themanganese may have migrated from the adhesion layer into the dielectric.

The foregoing description of the embodiments of the invention has beenpresented for the purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formsdisclosed. This description and the claims following include terms, suchas left, right, top, bottom, over, under, upper, lower, first, second,etc. that are used for descriptive purposes only and are not to beconstrued as limiting. For example, terms designating relative verticalposition refer to a situation where a device side (or active surface) ofa substrate or integrated circuit is the “top” surface of thatsubstrate; the substrate may actually be in any orientation so that a“top” side of a substrate may be lower than the “bottom” side in astandard terrestrial frame of reference and still fall within themeaning of the term “top.” The term “on” as used herein (including inthe claims) does not indicate that a first layer “on” a second layer isdirectly on and in immediate contact with the second layer unless suchis specifically stated; there may be a third layer or other structurebetween the first layer and the second layer on the first layer. Theembodiments of a device or article described herein can be manufactured,used, or shipped in a number of positions and orientations. Personsskilled in the relevant art can appreciate that many modifications andvariations are possible in light of the above teaching. Persons skilledin the art will recognize various equivalent combinations andsubstitutions for various components shown in the Figures. It istherefore intended that the scope of the invention be limited not bythis detailed description, but rather by the claims appended hereto.

What is claimed is:
 1. A method of fabricating an integrated circuitstructure, the method comprising: forming a dielectric layer; forming anopening in the dielectric layer, the opening having an upper portion anda lower portion; forming a cobalt plug in the lower portion of theopening; forming a manganese-based adhesion layer on sidewalls of theupper portion of the opening and on the cobalt plug; forming a cobaltfill material in the upper portion of the opening and on themanganese-based adhesion layer; and applying heat to reflow the cobaltfill material.
 2. The method of claim 1, wherein the cobalt plugcomprises at least 50% cobalt.
 3. The method of claim 2, wherein thecobalt plug further comprises one or more of Al, Ni, Cu, Ag, Au, Mn, Ti,V, Cr, Fe, Ta, W or Ru.
 4. The method of claim 1, wherein the cobaltplug comprises at least 90% cobalt.
 5. The method of claim 4, whereinthe cobalt plug further comprises one or more of Al, Ni, Cu, Ag, Au, Mn,Ti, V, Cr, Fe, Ta, W or Ru.
 6. The method of claim 1, wherein themanganese-based adhesion layer comprises a material selected from thegroup consisting of Mn, MnN, MnSixNy, and MnSixOy. The method of claim1, wherein the cobalt fill material consists essentially of cobalt. 8.The method of claim 1, wherein the cobalt fill material comprises 95+%cobalt with the remainder comprising one or more of Al, Ni, Cu, Ag, Au,Mn, Ti, V, Cr, Fe, Ta, W or Ru.
 9. The method of claim 1, wherein thecobalt fill material comprises a material different than the cobaltplug.
 10. The method of claim 1, wherein the cobalt fill materialconsists essentially of cobalt, the cobalt plug comprises at least 50%cobalt, the manganese-based adhesion layer comprises a material selectedfrom the group consisting of Mn, MnN, MnSixNy, and MnSixOy, and whereinthe cobalt fill material comprises a material different than the cobaltplug.
 11. A method of fabricating an integrated circuit structure, themethod comprising: forming a dielectric layer; forming an opening in thedielectric layer, the opening having an upper portion and a lowerportion, the upper portion having a width greater than a width of thelower portion; forming a cobalt plug in the lower portion of theopening; forming a manganese-based adhesion layer on sidewalls of theupper portion of the opening and on the cobalt plug; and forming acobalt fill material in the upper portion of the opening and on themanganese-based adhesion layer.
 12. The method of claim 11, wherein thecobalt plug comprises at least 50% cobalt.
 13. The method of claim 12,wherein the cobalt plug further comprises one or more of Al, Ni, Cu, Ag,Au, Mn, Ti, V, Cr, Fe, Ta, W or Ru.
 14. The method of claim 11, whereinthe cobalt plug comprises at least 90% cobalt.
 15. The method of claim14, wherein the cobalt plug further comprises one or more of Al, Ni, Cu,Ag, Au, Mn, Ti, V, Cr, Fe, Ta, W or Ru.
 16. The method of claim 11,wherein the manganese-based adhesion layer comprises a material selectedfrom the group consisting of Mn, MnN, MnSixNy, and MnSixOy.
 17. Themethod of claim 11, wherein the cobalt fill material consistsessentially of cobalt.
 18. The method of claim 11, wherein the cobaltfill material comprises 95+% cobalt with the remainder comprising one ormore of Al, Ni, Cu, Ag, Au, Mn, Ti, V, Cr, Fe, Ta, W or Ru.
 19. Themethod of claim 11, wherein the cobalt fill material comprises amaterial different than the cobalt plug.
 20. The method of claim 11,wherein the cobalt fill material consists essentially of cobalt, thecobalt plug comprises at least 50% cobalt, the manganese-based adhesionlayer comprises a material selected from the group consisting of Mn,MnN, MnSixNy, and MnSixOy, and wherein the cobalt fill materialcomprises a material different than the cobalt plug.